A) Field of the Invention
The present invention relates to a method of manufacturing a probe unit having leads disposed in parallel at a small pitch, each lead extending beyond the edge of a substrate to form an elastic beam. The probe unit is used, for example, for a conduction test of electrodes of a semiconductor integrated circuit, a liquid crystal panel or the like.
B) Description of the Related Art
A conduction test of a semiconductor integrated circuit, a liquid crystal panel or the like is performed in order to check whether the test sample operates normally satisfying the specification. This conduction test is performed, for example, by pressing the front end of a probe unit against electrodes disposed in parallel at the edge of a glass plate of a liquid crystal panel. It is therefore necessary that the front portions of leads of the probe unit formed on a substrate form elastic beams.
The pitch of the electrodes disposed at the edge of a liquid crystal panel is becoming smaller. The pitch of elastic beams of the front portions of leads of a probe unit is required correspondingly small.
The pitch of electrodes is presently 0.1 mm. A probe unit to be used with such electrodes is difficult to be formed with a punching machine. From this reason, etching or plating has been used for forming a probe unit.
Probe unit manufacture methods are disclosed, for example, in JP-A-8-015318. According to one method, two substrates are abutted together and a number of leads are grown by plating on the surface of the substrate to be disposed in parallel and traversing the two substrates. Next, one of the two substrates is removed from the leads extending on the surface of the substrate so that the front portions of leads extend beyond the edge of the other substrate to form elastic beams. According to the other method, a number of leads are grown by plating in parallel on the surface of one substrate. Next, the end portion of the substrate is cut so that the front portions of leads extend beyond the edge of the remaining substrate to form elastic beams.
Another probe unit manufacture method is disclosed in JP-A-7-199219. According to this method, a silicon oxide film is formed on a silicon substrate. The silicon oxide film is partially removed by etching to expose the surface of the silicon substrate on which elastic beams of probes are later formed. A metal film having a predetermined pattern is formed on the exposed silicon surface and oxide film. Leads of a probe unit are grown on the metal film by plating. Next, the exposed silicon substrate is removed by anisotropic etching so that the front portions of the leads extend beyond the edge of the remaining substrate to form elastic beams.
The first method disclosed in JP-A-8-015318 teaches some device of making a coupling force of a plated layer to a contact lead region of the substrate different from a coupling force to an elastic lead region of the substrate. However, there remains some problem that some tight contactness is required between a plated underlayer and the substrate in the elastic lead region when the plated underlayer is formed and when the plated layer is grown and that some peeling property is required when the substrate is removed from the leads. If the coupling force of the plated layer is too small, the plated layer is separated from the substrate because of stress generated during plating. The shape of a fine probe may be deformed or damaged. If the coupling force is high, the function of removing the substrate from leads becomes low and the leads may be deformed following the deformed shape of the substrate. If the single substrate is used and this substrate cannot be cut completely, elastic beams extending beyond the edge of the remaining substrate cannot be formed. It is necessary to cut the substrate without damaging the leads. This cutting is very difficult and there is a high possibility of damaging leads when the substrate is cut.
In a practical case, the substrate is cut to such a depth reaching near the leads so that the cutting blade does not contact the leads. After this cutting, the substrate is bent downward or upward about the cut to remove the end portion of the substrate. Since the cut had a finite depth, when the substrate was bent upward, the break positions became irregular because of the cut depth. Further, the substrate moves the lead front portions upward so that some elastic beams were deformed.
The irregularity of break positions was bigger when the substrate was bent downward than when it was bent upward. The lengths of elastic beams were irregular and the loads necessary for a predetermined bending amount were not able to be controlled. A bending work was not stable so that large forces were applied to some leads some of which were deformed.
The method described in JP-A-7-199219 requires to anisotropically etch the end portion of the substrate to form elastic beams. Therefore, the substrate is limited only to a silicon substrate. The insulating film such as a silicon oxide becomes essential. Various other substrates requested by users cannot be adopted.